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Magnetic Background Issues above 1Hz for CLIC beams

This study investigates the impact of magnetic background issues above 1 Hz on the CLIC beams, focusing on klystron performance and beam stability. It discusses the necessary tolerances for variable fields in critical components such as the main linac and long transfer lines. Measurements highlight the influence of external factors, including high voltage transmission lines and site power distribution on stray magnetic fields. Proposals for mapping and reducing these stray fields are also presented, aiming to minimize their effects on beam precision and emittance growth.

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Magnetic Background Issues above 1Hz for CLIC beams

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  1. Magnetic Background Issues above 1Hz for CLIC beams Cezary Jach CLIC2009

  2. 326 klystrons 33 MW, 139 ms combiner rings Circumferences delay loop 72.4 m CR1 144.8 m CR2 434.3 m drive beam accelerator 2.38 GeV, 1.0 GHz CR1 CR1 1 km delay loop CR2 326 klystrons 33 MW, 139 ms drive beam accelerator 2.38 GeV, 1.0 GHz 1 km delay loop CR2 decelerator, 24 sectors of 868 m BDS 2.75 km BDS 2.75 km BC2 BC2 245m 245m IP1 e- main linac , 12 GHz, 100 MV/m, 20.85 km e+ main linac TA R=120m TA R=120m 47.9 km CLIC 3 TeV booster linac, 9 GeV, 2 GHz or 4 GHz ? BC1 e- injector 2.4 GeV e+ injector, 2.4 GeV e+ DR 365m e- DR 365m

  3. Tolerance to variable fields • In the Main Linac • In the long transfer line of the Main Beam • Near the IP • In all cases, we must consider • Frequencies above 1 Hz • Quasi-static field (above tolerance, implies re-adjustment of the line)

  4. Main Linac & MB_LTL • Main Linac : B < 0.2 nTat f>1 Hz (To allow neat feed-back at 50 Hz - D. Schulte) • Long Transfer Line : • Adding fields of variable f to the FODO line • Track, get the beam displacement • From this, compute the tolerance , • corresponding to 10% emittance growth after filamentation • B≈ 0.01 nTat f>1 Hz Study by J. Snuverink (For incoherent addition by sector)

  5. Near the IP y ⊗ B Δ ⊗ x s Current to produce B, in a conductor parallel to the beam in the horizontal plane at r from the beam axis : L = 3.5 m

  6. Possible Sources of StrayMagnetic Field • High voltage transmission lines • Site power distribution system • Linac power distribution system • Electronics, vacuum pumps, compressors, etc. • Railroads • ?

  7. High voltage transmission lines • Along the Jura, both in F +CH • Still awaiting detailed data from EDF and EOS • Considering a generic case: +I -I ● ● +I -I ● ● 7m +I -I Even with the 1st-order cancellation offered by the 3 phases , it remains : ● ● Bx = 16 nTat (+300m,-100m)

  8. Coupling rejection

  9. Train Leakage Currents (LEP)* *"The Influence of Train Leakage Currents on LEP Dipole Field" - CERN SL 97-47

  10. Train Leakage Currents (2)

  11. Train Leakage Currents (3)

  12. Train Leakage Currents (4) Proportional to train leakage current Proportional to LEP vacuum chamber current ΔB/B ≈ 10-5

  13. FNAL data I - Courtesy of DmitriSergatskov Data taken in the A0 exp-hall In a ‘quiet’ office building : 10 × lower

  14. FNAL data II - Courtesy of DmitriSergatskov • Level ∼10 × above HV-network estimate

  15. Next Steps • Confirmation of stray magnetic field sensitivities • Stray magnetic field mapping • Proposals for stray magnetic field reduction methods • Local • general • Cost impact

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